pkg/logging: Fix HTTP logging middleware panic (#3922)

Signed-off-by: Frederic Branczyk <fbranczyk@gmail.com>

CHANGELOG.md

@@ -18,6 +18,7 @@ We use _breaking :warning:_ to mark changes that are not backward compatible (re
 
 ### Fixed
 - [#3204](https://github.com/thanos-io/thanos/pull/3204) Mixin: Use sidecar's metric timestamp for healthcheck.
+- [#3922](https://github.com/thanos-io/thanos/pull/3922) Fix panic in http logging middleware.
 
 ### Changed
 

pkg/logging/http.go

@@ -5,8 +5,8 @@ package logging
 
 import (
 	"fmt"
+	"net"
 	"sort"
-	"strings"
 
 	"net/http"
 	"time"
@@ -39,7 +39,12 @@ func (m *HTTPServerMiddleware) HTTPMiddleware(name string, next http.Handler) ht
 	return func(w http.ResponseWriter, r *http.Request) {
 		wrapped := httputil.WrapResponseWriterWithStatus(w)
 		start := time.Now()
-		port := strings.Split(r.Host, ":")[1]
+		_, port, err := net.SplitHostPort(r.Host)
+		if err != nil {
+			level.Error(m.logger).Log("msg", "failed to parse host port for http log decision", "err", err)
+			next.ServeHTTP(w, r)
+			return
+		}
 
 		decision := m.opts.shouldLog(fmt.Sprintf("%s:%s", r.URL, port), nil)
 

pkg/logging/http_test.go

@@ -0,0 +1,37 @@
+// Copyright (c) The Thanos Authors.
+// Licensed under the Apache License 2.0.
+
+package logging
+
+import (
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/go-kit/kit/log"
+	"github.com/thanos-io/thanos/pkg/testutil"
+)
+
+func TestHTTPServerMiddleware(t *testing.T) {
+	m := NewHTTPServerMiddleware(log.NewNopLogger())
+	handler := func(w http.ResponseWriter, r *http.Request) {
+		_, err := io.WriteString(w, "Test Works")
+		if err != nil {
+			t.Log(err)
+		}
+	}
+	hm := m.HTTPMiddleware("test", http.HandlerFunc(handler))
+
+	req := httptest.NewRequest("GET", "http://example.com/foo", nil)
+	w := httptest.NewRecorder()
+
+	hm(w, req)
+
+	resp := w.Result()
+	body, _ := ioutil.ReadAll(resp.Body)
+
+	testutil.Equals(t, 200, resp.StatusCode)
+	testutil.Equals(t, "Test Works", string(body))
+}